When you experience stress, a chain reaction happens in your body. Within seconds, your brain switches to alarm mode and prepares your body for action. This process happens through a collaboration between three parts: the hypothalamus, the pituitary gland and the adrenal glands. Together called the “stress axis”.
This stress response is primal and basically life-saving. The problem arises when the system is activated too often or for too long, such as with unprocessed trauma or chronic stress.
The stress axis: how does it work?
The stress response proceeds in a fixed order:
- Hypothalamus: detects danger and sends an alarm signal (CRF)
- Pituitary: receives the signal and releases a messenger substance (corticotropin/ACTH)
- Adrenal glands: produce the stress hormone cortisol
- Cortisol: prepares your body for action - fight or flight
Step by step through the stress response
Imagine: you are walking down the street and suddenly hear squealing brakes behind you. Even before you consciously realise what is happening, your brain has already sprung into action.
The hypothalamus, a small area deep in your brain, acts as the alarm centre. As soon as it detects danger through your senses or even threatening thoughts, it produces a substance called CRF (corticotropin-releasing factor). This is the starting signal of the stress response.
The CRF travels to the pituitary gland, a pea-sized gland that hangs below your brain. The pituitary responds by releasing corticotropin (also known as ACTH) into the blood. This hormone then travels to the adrenal glands, two small glands that sit on top of your kidneys.
The adrenal glands then produce cortisol, the main stress hormone. Cortisol makes your body ready for action: your heart rate speeds up, your muscles tighten, your senses sharpen and your blood sugar rises to release energy. Functions that are not needed at that moment, such as digestion and immune response, are temporarily suppressed.
The brake on the system
In a healthy situation, this system has a built-in brake. When enough cortisol is circulating in your blood, it signals back to the hypothalamus and pituitary gland: “It's enough, you can stop.” This is called the negative feedback loop. The production of stress hormones is slowed down and your body returns to rest.
In people with chronic stress or PTSD, this brake often does not work as well. The stress system remains active even when there is no acute danger. The consequences are noticeable: persistent fatigue, sleep problems, concentration problems and, in time, even physical complaints. Your body remains in alarm mode, with all its exhausting consequences.
Understanding this mechanism also reveals why relaxation techniques and trauma treatment are so important: they help the stress system learn to switch off again when it is safe to do so.
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